Japanese knotweed
Polygonum cuspidatum 'Spectabile'
Not currently listed at our partner nurseries.
Essentials
At a Glance
Plant Type
Perennial
Height
60 inches
Width
60 inches
Light
Full Sun, Partial Sun
Zones
4, 5, 6, 7, 8, 9
Water
Moderate
Humidity
Average
Lifespan
Perennial
Native To
East Asia
Toxicity
Non-toxic
The Story
Plant Bio
A vigorous, spreading perennial with large, heart-shaped leaves variegated with cream and pink. While visually striking, it is a cultivar of the highly invasive Japanese Knotweed and should be planted with extreme caution in a contained area, if at all. The 'Spectabile' cultivar features attractive variegation but retains the aggressive, spreading root system of the species, which can damage structures and outcompete native flora.
Bloom Period:
Uses & Benefits:
Marketplace
Where to Buy
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Planting
How to Grow
- Tuck seeds into moist soil in early spring.
- Water regularly to keep soil evenly moist.
- Provide full sun for optimal growth.
- Mulch around base to retain moisture.
- Divide in early spring every 3-4 years.
- Prune back after flowering to maintain shape.
Pro Tip
Plant in well-drained soil and avoid overwatering to prevent root rot.
Keep It Thriving
Care Guide
Do
- Water deeply during dry spells 🌱
- Prune to control size and shape
- Fertilize in early spring with balanced fertilizer
- Mulch to conserve moisture
Don't
- Avoid overwatering ❌
- Don't plant in poorly drained areas
- Never allow soil to dry out completely
- Avoid excessive fertilization
Seasonal Care Calendar
| Task | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pest Check | ||||||||||||
| Plant | ||||||||||||
| Prune |
Watch Out For
Pests & Diseases
Common Pests
Common Diseases
In the Garden
Landscape Uses & Companions
Landscape Uses
Companion Plants
Multiply
Propagation Methods
Good to Know
Common Questions
Japanese knotweed questions
What zones can Japanese knotweed grow in?
Japanese knotweed is hardy in USDA Zones 4–9. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.
Is Japanese knotweed deer resistant?
Not reliably. Deer may browse Japanese knotweed, especially tender spring growth — plan on repellents or fencing where pressure is high.
When does Japanese knotweed bloom?
Japanese knotweed typically blooms in late summer through late fall. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.
Does Japanese knotweed need full sun?
Japanese knotweed does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.
Is Japanese knotweed drought tolerant?
Yes — once established (usually after the first full season), Japanese knotweed handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.
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Grow Japanese knotweed with confidence
See it in a design of your actual yard, get zone-matched care reminders, and track it season by season in your garden journal.
